ABSTRACT

In order to understand the influence of the methyl group in the stability of the indole unit, the standard (p 1/4 0:1 MPa) molar enthalpies of formation of 1-, 2-, and 3-methylindoles, in the gaseous phase, were determined at T = 298.15 K. For that, combustion calorimetry was used to determine the massic energies of combustion and consequently the standard molar enthalpies of formation in the condensed phase, and Calvet microcalorimetry was employed to measure the standard molar enthalpy of phase transition (vaporization for the liquid 1-methylindole and sublimation for the other two solid compounds). The G3(MP2)//B3LYP composite approach was used to calculate the gas-phase enthalpies of formation, at T = 298.15 K, of all possible single methylated indoles using four different working reactions. The enthalpies calculated for the 1-, 2-, and 3-methylindoles are in excellent agreement with the values derived from the experimental work.

Compounds

#	Formula	Name
1	CO2	carbon dioxide
2	N2	nitrogen
3	H2O	water
4	O2	oxygen
5	C9H9N	1-methylindole
6	C9H9N	2-methylindole
7	C9H9N	3-methyl-1H-indole

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Phase	Method	#Points
POMD	5	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Liquid	Drop calorimetry	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Calvet microcalorimetry	1
POMD	6	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Calvet microcalorimetry	1
POMD	7	Molar enthalpy, kJ/mol ; Gas	Temperature, K; Gas	Gas Crystal	Drop calorimetry	1
POMD	7	Molar enthalpy of transition or fusion, kJ/mol ; Crystal	Temperature, K; Crystal	Crystal Gas	Calvet microcalorimetry	1
RXND	5 1 2 3 4	Specific internal energy of reaction at constant volume, J/g			Static bomb calorimetry	1
RXND	6 1 2 3 4	Specific internal energy of reaction at constant volume, J/g			Static bomb calorimetry	1
RXND	7 1 2 3 4	Specific internal energy of reaction at constant volume, J/g			Static bomb calorimetry	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Combined experimental and computational study of the energetics of methylindoles

Ribeiro da Silva, M. A. V.[Manuel A. V.], Cabral, J. I. T. A.[Joana I. T. A.], Gomes, J. R. B.[Jose R.B.]

ABSTRACT